RTV or No?

[Tomfrmnh]

Okay. Just pulled the engine to change the gasket on pump housing. I thoroughly cleaned both surfaces. Notice some paint missing on the pump side and minor scoring and some minor scoring on the engine manifold side. (Right in the vicinity of where it was leaking). Will the gasket cover the scoring and missing paint? The adhesive on the gasket goes down on the pump housing but not sure about the engine side, especially since that is where it was leaking. Is RTV a "no no"? ill try and upload some pics

 

[Sportster-2001-951C-Stock]

Is this the flange where the motor sits on the pump? What prompted this repair?

I guess RTV might work but if this was a leak to begin with and the flange surfaces are corroded or damaged I might consider filling the damage to make a new flat surface by using an epoxy paste such as Marine-TEX or JB-Weld (not JB Quick).

Another great polyurethane adhesive is 3M-5200 but be careful to use an adhesion barrier on one dry surface (such as a gasket, wax paper, etc.) b/c 5200 will permanently adhere two surfaces together like you wouldn't believe when you decide to disassemble. Besides, 5200 requires several days of cure.

Motoseal parting line sealer might work as well, or "The Right Stuff" in the case the surface damage is minor. Whatever is done, the gasket needs enough clamping force support on both sides so it won't blow out.

 

[Tomfrmnh]

Thanks for the response.

I had a leak in the back where the motor mounts to the pump flange. I was able to get back there and take some video. You could see where it coming through the seal. It was tough to see as it is almost at the very aft part of the flange It looks like when the motor was mounted (whether at the factory or DIY fix) the tilt in the engine when lowering one of the studs scraped the motor side flange. Right under the exhaust Not a real deep scrape but curiously enough it was right where I saw the leaking on the video. JB weld I worry about not getting an even coating and creating a high spot. You think JB Weld overv RTv? Really only want to do this once. Those nuts are a PIA to get to.

 

[Sportster-2001-951C-Stock]

The flange has a gasket clamped in it so I guess you're using a new gasket. If only a paint scrape from a stud then a simple sealer such as motoseal or "The Right Stuff" might be sufficient as the paint is probably ~0.010" thick at most. Or you could try RTV....

The idea of using JB-WELD for more than missing paint is to degrease the surface for repair using acetone, block-sand away lose or peeling paint and to scuff the exposed aluminum degrease the surface using acetone and apply the epoxy to fill the damaged gouge and while curing place a flat object on wax paper over the area to create a flat surface and if necessary the JB-WELD can be block-sanded or filed flat as well. A metal straight edge should reveal dips or high spots.

If using JB-WELD, I suppose you could simply apply before placing the gasket on then drop the motor on and clamp it down while the JB cures. Kinda depends on how much damage there is on the flange. I like to see the gasket held in place by clamping force but just a scratch might allow a leak without blowing out the gasket.

Perhaps just some "The right stuff" as sealer, sometimes a new gasket is thick enough to conform to the imperfections without any sealers if the surfaces are in reasonable condition.

Look very carefully for cracks, JB can fill them if the grease and oil is first washed away.

I've never been a huge fan of RTV due to the adhesion is rarely what I'd consider good, so admittedly I'm a little biased.

 

[Tomfrmnh]

Great stuff. Thank you. Yes, definitely using a new gasket (and o-rings). You talked me out of the RTV. I will look into motto seal for the engine side and probably go with the JB for the pump side. I didn't see any cracks and both surfaces have been thoroughly cleaned with acetone. Thanks again for the advise. It is much appreciated.

Tom

 

[Tomfrmnh]

The flange has a gasket clamped in it so I guess you're using a new gasket. If only a paint scrape from a stud then a simple sealer such as motoseal or "The Right Stuff" might be sufficient as the paint is probably ~0.010" thick at most. Or you could try RTV....

The idea of using JB-WELD for more than missing paint is to degrease the surface for repair using acetone, block-sand away lose or peeling paint and to scuff the exposed aluminum degrease the surface using acetone and apply the epoxy to fill the damaged gouge and while curing place a flat object on wax paper over the area to create a flat surface and if necessary the JB-WELD can be block-sanded or filed flat as well. A metal straight edge should reveal dips or high spots.

If using JB-WELD, I suppose you could simply apply before placing the gasket on then drop the motor on and clamp it down while the JB cures. Kinda depends on how much damage there is on the flange. I like to see the gasket held in place by clamping force but just a scratch might allow a leak without blowing out the gasket.

Perhaps just some "The right stuff" as sealer, sometimes a new gasket is thick enough to conform to the imperfections without any sealers if the surfaces are in reasonable condition.

Look very carefully for cracks, JB can fill them if the grease and oil is first washed away.

I've never been a huge fan of RTV due to the adhesion is rarely what I'd consider good, so admittedly I'm a little biased.

Thank you Sportster-2001-951C-Stock

I decided to go with JB on both surfaces like you suggested. Had two leave for two weeks right after I I finished the job. I came back yesterday and double checked the mounting bolts and gave it a try.....fixed! Thanks for the help. This Seemed like a big job But wasn't too bad. I did a lot of reading on gasket sealing. Seems like all the literature said the same. Small Imperfections on the clamping surfaces can usually be sealed by the gasket, however, any imperfection that extends across the gasket surface is usually where the gasket fails. That's what I had right where it was leaking. A fairly deep scratch across the flange. (I'm pretty sure Caused by the engine surface flange scraping on the mounting stud during last install).

Now on to the next job.....

 

[Sportster-2001-951C-Stock]

Nice, glad you're back up and running, Tom. Ahh, forgot to mention another method is simply by using double gaskets to compensate for voids, case by case circumstances judgment call of course. JB makes for a good gouge and even crack filler on these parting surfaces I believe, it's done me well many times in similar circumstances.

So good luck, I'm confident you have a good repair.